1. Field of the Invention
The invention relates to an inductive device, comprising a soft magnetic core which consists of two E-shaped core halves, each of which comprises three parallel limbs which are interconnected by a yoke. The core halves are arranged one against the other by way of the free ends of the limbs, the central limbs being surrounded by a coil former on which a winding is provided. The outer limbs extend between an upper boundary plane and a lower boundary plane, which boundary planes extend parallel to the longitudinal directions of the limbs and the yokes. The distance between the boundary planes is determined by the dimension of the outer limbs in the direction perpendicular to the boundary planes, that being the height of the outer limbs, which height is greater than the height of the central limbs. The central limbs have a symmetry plane extending parallel to the boundary planes.
The inductive device can be, for example a transformer or a choke coil.
2. Description of the Related Art
A transformer of this kind is known from U.S. Pat. No. 4,760,366. Such transformers are intended particularly for mounting on a printed circuit board, the boundary planes then extending parallel to the plane of the board. The lower boundary plane is then formed by the boundary plane nearest to the board. The coil former may be provided with a connection strip with connection pins which are connected to lead-outs of the winding and which project below the lower boundary plane in a direction perpendicular to the boundary planes. The lower boundary of the coil former then rests against the surface of the board. The reason the height of the central limb is smaller than the height of the outer limbs is that the structural height of the core may then be smaller than in conventional E-cores. This is important because printed circuit boards are often mounted one over the other and the distance between neighbouring boards must then be as small as possible, for example 25.4 mm. Because the transformer is often the largest (highest) component on such a board, its height must be as small as possible.